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81.
The paper briefly describes an electro-optical system for counting of dust particles, which is based on the scattering phenomena.Utilizing the scattering of light by various size particles present in the environment, various particle counting techniques have been developed in order to measure the scattered intensity of light. Light scatters in all directions but much more in the so-called near forward direction 17∘ off axis, at 163∘ from the light source in the visible range.On the basis of two techniques, the right angle and forward angle scattering, opto-mechanical systems have been developed which measure scattered intensity and particulate matter. The forward scattering Nephelometer is more sensitive and therefore is more suitable for pollution monitoring than the right angle scattering Nephelometer. Whereas the right angle scattering Nephelometer has the utility in extremely low concentration in ppb level owing to the excellent light trap efficiency in comparison to forward scattering Nephelometer. In this paper measurement techniques and measurement results associated with design and development of a real time particle analyser are also discussed. 相似文献
82.
83.
Roy BK Prasad R Gunjan 《Journal of environmental biology / Academy of Environmental Biology, India》2010,31(5):567-573
The extent of accumulation of some heavy metals in root and aerial plant parts, total chlorophyll, protein and yield of C. cajan exposed to mine spoil were investigated. Chlorophyll and protein level on the control site increased from the basal level to 1.49 fold and 1.92 fold respectively on 150 d and attained a plateau within 210 d. The maximum decline in leaf protein and yield in selected mine spoil has been observed 37% (18.46 mg g(-1) fresh wt) and 76% at 150 d and maintained a slight decline when duration was extended up to 210 d as compared to control. Whereas in case of photo pigment content (Chlorophyll a and b) the maximum reduction was almost 42% (0.786 mg g(-1) fresh wt) during 210 d from its basal level. Plant tissues have accumulated maximum level of selected cations in control and mine spoil in the order (Fe > Mn > Zn > Cu > Pb > Ni > Cr > Cd). Metal accumulation in different plant parts was observed in the decreasing order roots > shoots > leaves > seeds. Invariably high accumulation of such cations in roots overshoots indicated accumulation, retention or restricted translocation from root to shoot. The metal share of seed varied from 1.3-39.5 fold as compared to their respective controls but their amount was quite below the toxic range. Thus the present work explores the metal accumulation in the plant tissues. 相似文献
84.
Modified Fenton's processes for effective in‐situ chemical oxidation—Laboratory and field evaluation
Prasad K. Kakarla Thomas Andrews Richard S. Greenberg David S. Zervas 《补救:环境净化治理成本、技术与工艺杂志》2002,12(4):23-36
Fenton's reagent in its conventional form, although effective for contaminant treatment, is impractical from an in‐situ field application perspective due to low pH requirements (i.e., pH 3‐4), and limited reagent mobility when introduced into the subsurface. Modified Fenton's processes that use chelated‐iron catalysts and stabilized hydrogen peroxide have been developed with the goal of promoting effective in‐situ field application under native pH conditions (i.e., pH 5‐7), while extending the longevity of hydrogen peroxide. Laboratory experiments conducted in soil columns packed with organic soil to compare modified Fenton's catalysts with conventional catalysts (acidified iron [II]) indicated superior mobility and sorption characteristics for modified Fenton's catalysts. Furthermore, the acidic pH of a conventional catalyst was buffered to the native soil range, leading to increased iron precipitation/adsorption following permeation through the soil column. The chelates present within the modified Fenton's catalyst showed greater affinity toward iron compared with the native soil and, hence, minimized iron loss through adsorption during the permeation process even at pH 5‐7. Field effectiveness of the modified Fenton's process was demonstrated at a former dry‐cleaning facility located in northeast Florida. Preliminary laboratory‐scale experiments were conducted on soil‐slurry and groundwater samples to test the process efficacy for remediation of chlorinated solvents. Based on successful experimental results that indicated a 94 percent (soil slurry) to 99 percent (groundwater) reduction of cis‐1,2‐DCE, PCE, and TCE, a field‐scale treatment program was initiated utilizing a plurality of dual‐zone direct push injection points installed in a grid fashion throughout the site. Results of treatment indicated a 72 percent reduction in total chlorinated contamination detected in the site groundwater following the first injection event; the reduction increased to 90 percent following the second injection event. © 2002 Wiley Periodicals Inc. 相似文献
85.
Biomass burning associated with shifting cultivation areas from the northeastern region of India is an important source of trace gas emissions in the Southeast Asian region. In the present study, satellite data pertaining to IRS-P4 OCM data and DMSP-OLS has been used to quantify the intensity, areal extent and amount of biomass burnt in the northeastern region states at district level. Trace gas emissions have been quantified both by using IPCC based emission ratios and ground based emission ratios obtained from field based studies. Areal estimates with respect to shifting cultivation areas from IRS-P4 OCM satellite data of 4th April 2000 suggested nearly 112.99 km2 of the northeastern region of India affected due to shifting cultivation. In the study, DMSP OLS nighttime data has been used to capture the real time fires during the dry season. The results suggested high amount of fires during the March season when compared to April and May. Using the emission ratios obtained from the ground-based studies and IPCC emission ratios, the emissions for the individual non-CO2 trace gases have been computed in a GIS framework using the biomass data, combustion factors and emission ratios. Results suggested emissions of 2.063 Mt CH4, 17.94 Mt CO, 1.419 Mt N2O, and 51.28 Mt NO
x
and 2.643 Mt release of CH4, 3.7204 Mt CO, 0.145 Mt N2O, and 8.477 Mt NO
x
, respectively, from biomass burning due to shifting cultivation for the year 2000, from the northeastern region in India. The study highlights the importance of Satellite Remote sensing data and GIS in quantifying the trace gas emissions from biomass burning. 相似文献
86.
87.
Prasad SK Vyas S 《Journal of environmental biology / Academy of Environmental Biology, India》2001,22(2):129-132
The possible effects of EMFs on 100 workers were studied by means of structured interview and rating of subjective symptoms. As control 41 sewing machine operators and assembly workers were chosen, interviewed and likewise tested. The present Indian ceiling value of 250 Tesla for the equivalent power density was exceeded in more than 50% of the machines. The highest leakage fields, for EMFs, were found near machines, which gave a high exposure to the hands. Eye irritation complaints were reported by 40% of the workers. The fertility outcome did not show any significant result. 相似文献
88.
We have examined the effect of Hg2+ ions on DNA, RNA and collagen synthesis in organ cultures of neo-natal rat lungs. These cultures exhibit many biochemical characteristics of lung in vivo and they continue to synthesize macromolecules at increasing rates up to 6 days. When these cultures were exposed to 1.0μM HgC12, the synthesis of DNA was stimulated nearly 3-fold after 72 hr of exposure followed by a decline at 120 hr reflecting cumulative cytotoxicity. Higher concentrations were inhibitory at all times. A nearly 3-fold increase in RNA synthesis occurred after 24 hr exposure to 1.0 μM HgC12 and at 72 hr the cultures continued to synthesize RNA at rates comparable to control. There was a decrease in RNA synthesis at 120 hr. Increased collagen synthesis was observed at concentrations up to 10 μM and at all times. The maximal increase, 2–3 fold, occurred at 120 hr in cultures exposed to 0.1 M. These studies suggest that Hg2+-induced cell injury in lung organ cultures elicits a reparative response characterized by increased collagen synthesis. This is similar to chemically induced tissue-injury in lungs in vivo. The relevance of these data to the mechanism of induced pulmonary fibrosis is discussed. These studies also point to the usefulness of organ cultures for studying pulmonary toxicity of environmental agents. 相似文献
89.
Emerging approaches to water resources development and management typically highlight equity and productivity as two main objectives. In the context of integrated water resources management within a river basin, managers and stakeholders often need a comparative assessment of different options for water augmentation and/or allocation. Pitting such options against predefined objectives, such as equity and productivity, requires an assessment of the effects that available options will have on these objectives. Available documentation indicates that not only does the interpretation of such objectives vary widely, but also the available methods for assessing equity and productivity run into significant limitations in the availability of adequate data. This limitation has largely kept decision makers from gaining a comprehensive overview of equity and productivity scenarios, whether within or across sectors, that could facilitate better‐informed decisions. To address this methodological gap, this article scrutinizes different notions associated with equity and water productivity, and limitations in prevalent assessment methods with the view to develop and demonstrate pragmatic methodologies for assessing equity and productivity in data‐scarce contexts. The discussion and findings are based on a review of relevant literature and empirical and consultative research work in the Olifants River basin in South Africa. The demonstrated methodologies for assessing equity and productivity, besides being useful in data‐scarce contexts, are insightful for initiating several policy measures and also for exploring the relationship between equity and water productivity. 相似文献
90.
Rajendra K. Pachauri 《Natural resources forum》1990,14(4):319-325
Much of the rural population of the developing countries is poor and depends on agriculture for its living. One means of improving the standard of living of such poor peoples is through the introduction of modern more intensive and therefore more productive agricultural methods. Such methods will require energy intensification. The resulting increase in energy demand particularly electrical energy, will be very large, especially because the rural areas are least able to benefit from energy saving technologies. 相似文献